<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            background: red;
            animation:kewinrun2 1s linear  infinite ;

            /* infinite 无限次进行执行 */
        }

        /* 声明动画 */
        @keyframes kewinrun1 {
            from{
              width: 200px;
              height: 200px;
              background: red;
            }
            to{
               width: 400px;
               height: 600px;
               background: green;
            }
        }
        @keyframes kewinrun2 {
            0%{
              width: 200px;
              height: 200px;
              background: red;
            }
            50%{
                width: 400px;
                height: 500px;
                background: blue;
            }
            100%{
               width: 400px;
               height: 600px;
               background: green;
            }
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>